Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $147.36   13.710%   $167.5631   $167.56   $167.55   $167.60  
  Purchase #2 $185.84   8.321%   $201.3037   $201.30   $201.30   $201.30  
  Purchase #3 $49.93   8.755%   $54.3014   $54.30   $54.30   $54.30  
  Purchase #4 $59.68   13.590%   $67.7905   $67.79   $67.80   $67.80  
  Purchase #5 $187.48   3.163%   $193.41   $193.41   $193.40   $193.40  
  Purchase #6 $102.65   5.383%   $108.1756   $108.18   $108.20   $108.20  
  Purchase #7 $232.91   9.691%   $255.4813   $255.48   $255.50   $255.50  
  7 purchase totals = $965.85       $1,048.0256   $1,048.02   $1,048.05   $1,048.10